President Serzh Sarkisian praised the U.S. role in the Nagorno-Karabakh peace process and Washington’s contribution to broader regional security when he met with U.S. Vice President Joe Biden in Washington late on Thursday.

The two men held talks in the White House ahead of a global nuclear security summit hosted by President Barack Obama.

Sarkisian is among around 50 heads of state that were invited to the annual summit. Russian President Vladimir Putin is boycotting it, apparently unwilling to join in a U.S.-dominated gathering at a time of increased tensions between Washington and Moscow.

“The Vice President stressed that the United States is committed to a democratic, prosperous, and secure Armenia at peace with its neighbors,” the White House said in a readout of the meeting with Sarkisian. “The Vice President thanked President Sarkisian for welcoming more than 20,000 Syrian refugees.”

A statement by the Armenian presidential press office said Biden and Sarkisian discussed Armenia’s relationship with the United States, international efforts to resolve the Nagorno-Karabakh conflict and the situation in Syria.

Sarkisian was reported to reaffirm his view that U.S.-Armenian relations are now “at their highest level in their history.” He spoke of deepening bilateral political, economic and security ties.

“Serzh Sarkisian also attached great importance to the U.S. role in maintaining peace and stability in the region and, in particular, the active U.S. involvement in the process of a peaceful resolution of the Nagorno-Karabakh conflict,” said the statement.

Azerbaijani President Ilham Aliyev, who is also takin part in the summit, discussed the unresolved dispute with U.S. Secretary of State John Kerry in Washington on Wednesday. “We want to see an ultimate resolution of the frozen conflict of Nagorno-Karabakh that needs to be a negotiated settlement and something that has to be worked on over time,” Kerry said after the talks.

“We are grateful to the U.S. government for their efforts in finding ways to resolve long-lasting conflict between Armenia and Azerbaijan,” Aliyev said for his part.

The Azerbaijani leader blasted the U.S. and the two other mediating powers, Russia and France, as recently as on March 19. In a speech in Baku, he claimed that the three co-chairs of the OSCE Minsk Group are “helping to freeze the conflict” and thus siding with Armenia.

According to the White House, Biden “expressed concern about continued violence, called for dialogue, and emphasized the importance of a comprehensive settlement for the long-term stability, security, and prosperity of the region.”

The mediators did not plan to organize a meeting of Sarkisian and Aliyev on the sidelines of the Washington summit. The two leaders failed to revive the peace process when they last met in Switzerland in December.

Foreign Minister Edward Nalbandian, who accompanied Sarkisian on the trip, met with James Warlick, Washington’s chief Karabakh negotiator, in the U.S. capital on Thursday.